As used in this description, the term “lens” refers to an optical device that passes and focuses light and may be a single element (piece of glass) or a plurality of elements (pieces of glass). A “corrected lens” refers to a lens system (multiple elements) which has been constructed to focus every point of light from a specimen onto an image plane (essentially free from spherical and chromatic aberrations). An “uncorrected lens” refers to a lens which, in forming an image of a specimen, focuses some light from the specimen at locations other than the corresponding point at the image plane (has some spherical and chromatic aberrations, or other type of distortion).
The quality of images produced by an optical system with lenses is largely dependent on the quality of the objective lens. One measure of the quality of a lens is the degree to which it is free of spherical and chromatic aberrations. The higher quality the lens, the less distortion introduced in the image formed by the lens. Lens aberrations are naturally-occurring because of the laws of refraction of light, and when lenses bend light at extreme angles, significant aberrations are produced. Good corrected lenses, such as PlanApo objective lenses, for example, are very expensive because they require a large number of precisely manufactured elements to correct for the naturally-occurring aberrations. Very high quality microscope lenses, for example, normally require as many as 10 or 12 different lens elements, each precisely manufactured and assembled, in order to eliminate aberrations and produce distortion-free images.
The universally accepted design desiderata for eliminating spherical and chromatic aberration in lenses is to build a lens that focuses all the rays of light from the specimen plane that pass through it onto a single flat (2D) image plane. It is from this 2D image plane that light values are detected for use in creating a digital image. For lenses to approach this perfection, they must be complex (multiple elements) and precisely manufactured.
Digital imaging technology is becoming the standard for imaging devices such as cameras, microscopes and telescopes. The combination of optics, robotics and computers has revolutionized the way we view the world around us. Image analysis programs and deconvolution software have enabled powerful manipulation of the images, such as removing out-of-focus blur and creating 3-dimensional images from a series of 2-dimensional optical sections.
The present invention teaches novel methods and apparatus for increasing the image quality of an image-forming optical system utilizing uncorrected lenses. By using digital manipulation techniques in connection with detection in a 3D space (and not just a 2D plane), the present invention enables an optical system to produce high-quality images essentially free from distortions, such as spherical and chromatic aberrations, without using corrected lenses.